drivers/tty/vt/vc_screen.c

   1 /*
   2  * linux/drivers/char/vc_screen.c
   3  *
   4  * Provide access to virtual console memory.
   5  * /dev/vcs0: the screen as it is being viewed right now (possibly scrolled)
   6  * /dev/vcsN: the screen of /dev/ttyN (1 <= N <= 63)
   7  *            [minor: N]
   8  *
   9  * /dev/vcsaN: idem, but including attributes, and prefixed with
  10  *      the 4 bytes lines,columns,x,y (as screendump used to give).
  11  *      Attribute/character pair is in native endianity.
  12  *            [minor: N+128]
  13  *
  14  * This replaces screendump and part of selection, so that the system
  15  * administrator can control access using file system permissions.
  16  *
  17  * aeb@cwi.nl - efter Friedas begravelse - 950211
  18  *
  19  * machek@k332.feld.cvut.cz - modified not to send characters to wrong console
  20  *       - fixed some fatal off-by-one bugs (0-- no longer == -1 -> looping and looping and looping...)
  21  *       - making it shorter - scr_readw are macros which expand in PRETTY long code
  22  */
  23
  24 #include <linux/kernel.h>
  25 #include <linux/major.h>
  26 #include <linux/errno.h>
  27 #include <linux/tty.h>
  28 #include <linux/interrupt.h>
  29 #include <linux/mm.h>
  30 #include <linux/init.h>
  31 #include <linux/vt_kern.h>
  32 #include <linux/selection.h>
  33 #include <linux/kbd_kern.h>
  34 #include <linux/console.h>
  35 #include <linux/device.h>
  36 #include <linux/sched.h>
  37 #include <linux/fs.h>
  38 #include <linux/poll.h>
  39 #include <linux/signal.h>
  40 #include <linux/slab.h>
  41 #include <linux/notifier.h>
  42
  43 #include <asm/uaccess.h>
  44 #include <asm/byteorder.h>
  45 #include <asm/unaligned.h>
  46
  47 #undef attr
  48 #undef org
  49 #undef addr
  50 #define HEADER_SIZE     4
  51
  52 #define CON_BUF_SIZE (CONFIG_BASE_SMALL ? 256 : PAGE_SIZE)
  53
  54 struct vcs_poll_data {
  55         struct notifier_block notifier;
  56         unsigned int cons_num;
  57         bool seen_last_update;
  58         wait_queue_head_t waitq;
  59         struct fasync_struct *fasync;
  60 };
  61
  62 static int
  63 vcs_notifier(struct notifier_block *nb, unsigned long code, void *_param)
  64 {
  65         struct vt_notifier_param *param = _param;
  66         struct vc_data *vc = param->vc;
  67         struct vcs_poll_data *poll =
  68                 container_of(nb, struct vcs_poll_data, notifier);
  69         int currcons = poll->cons_num;
  70
  71         if (code != VT_UPDATE)
  72                 return NOTIFY_DONE;
  73
  74         if (currcons == 0)
  75                 currcons = fg_console;
  76         else
  77                 currcons--;
  78         if (currcons != vc->vc_num)
  79                 return NOTIFY_DONE;
  80
  81         poll->seen_last_update = false;
  82         wake_up_interruptible(&poll->waitq);
  83         kill_fasync(&poll->fasync, SIGIO, POLL_IN);
  84         return NOTIFY_OK;
  85 }
  86
  87 static void
  88 vcs_poll_data_free(struct vcs_poll_data *poll)
  89 {
  90         unregister_vt_notifier(&poll->notifier);
  91         kfree(poll);
  92 }
  93
  94 static struct vcs_poll_data *
  95 vcs_poll_data_get(struct file *file)
  96 {
  97         struct vcs_poll_data *poll = file->private_data;
  98
  99         if (poll)
 100                 return poll;
 101
 102         poll = kzalloc(sizeof(*poll), GFP_KERNEL);
 103         if (!poll)
 104                 return NULL;
 105         poll->cons_num = iminor(file->f_path.dentry->d_inode) & 127;
 106         init_waitqueue_head(&poll->waitq);
 107         poll->notifier.notifier_call = vcs_notifier;
 108         if (register_vt_notifier(&poll->notifier) != 0) {
 109                 kfree(poll);
 110                 return NULL;
 111         }
 112
 113         /*
 114          * This code may be called either through ->poll() or ->fasync().
 115          * If we have two threads using the same file descriptor, they could
 116          * both enter this function, both notice that the structure hasn't
 117          * been allocated yet and go ahead allocating it in parallel, but
 118          * only one of them must survive and be shared otherwise we'd leak
 119          * memory with a dangling notifier callback.
 120          */
 121         spin_lock(&file->f_lock);
 122         if (!file->private_data) {
 123                 file->private_data = poll;
 124         } else {
 125                 /* someone else raced ahead of us */
 126                 vcs_poll_data_free(poll);
 127                 poll = file->private_data;
 128         }
 129         spin_unlock(&file->f_lock);
 130
 131         return poll;
 132 }
 133
 134 /*
 135  * Returns VC for inode.
 136  * Must be called with console_lock.
 137  */
 138 static struct vc_data*
 139 vcs_vc(struct inode *inode, int *viewed)
 140 {
 141         unsigned int currcons = iminor(inode) & 127;
 142
 143         WARN_CONSOLE_UNLOCKED();
 144
 145         if (currcons == 0) {
 146                 currcons = fg_console;
 147                 if (viewed)
 148                         *viewed = 1;
 149         } else {
 150                 currcons--;
 151                 if (viewed)
 152                         *viewed = 0;
 153         }
 154         return vc_cons[currcons].d;
 155 }
 156
 157 /*
 158  * Returns size for VC carried by inode.
 159  * Must be called with console_lock.
 160  */
 161 static int
 162 vcs_size(struct inode *inode)
 163 {
 164         int size;
 165         int minor = iminor(inode);
 166         struct vc_data *vc;
 167
 168         WARN_CONSOLE_UNLOCKED();
 169
 170         vc = vcs_vc(inode, NULL);
 171         if (!vc)
 172                 return -ENXIO;
 173
 174         size = vc->vc_rows * vc->vc_cols;
 175
 176         if (minor & 128)
 177                 size = 2*size + HEADER_SIZE;
 178         return size;
 179 }
 180
 181 static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
 182 {
 183         int size;
 184
 185         console_lock();
 186         size = vcs_size(file->f_path.dentry->d_inode);
 187         console_unlock();
 188         if (size < 0)
 189                 return size;
 190         switch (orig) {
 191                 default:
 192                         return -EINVAL;
 193                 case 2:
 194                         offset += size;
 195                         break;
 196                 case 1:
 197                         offset += file->f_pos;
 198                 case 0:
 199                         break;
 200         }
 201         if (offset < 0 || offset > size) {
 202                 return -EINVAL;
 203         }
 204         file->f_pos = offset;
 205         return file->f_pos;
 206 }
 207
 208
 209 static ssize_t
 210 vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 211 {
 212         struct inode *inode = file->f_path.dentry->d_inode;
 213         unsigned int currcons = iminor(inode);
 214         struct vc_data *vc;
 215         struct vcs_poll_data *poll;
 216         long pos;
 217         long attr, read;
 218         int col, maxcol, viewed;
 219         unsigned short *org = NULL;
 220         ssize_t ret;
 221         char *con_buf;
 222
 223         con_buf = (char *) __get_free_page(GFP_KERNEL);
 224         if (!con_buf)
 225                 return -ENOMEM;
 226
 227         pos = *ppos;
 228
 229         /* Select the proper current console and verify
 230          * sanity of the situation under the console lock.
 231          */
 232         console_lock();
 233
 234         attr = (currcons & 128);
 235         ret = -ENXIO;
 236         vc = vcs_vc(inode, &viewed);
 237         if (!vc)
 238                 goto unlock_out;
 239
 240         ret = -EINVAL;
 241         if (pos < 0)
 242                 goto unlock_out;
 243         poll = file->private_data;
 244         if (count && poll)
 245                 poll->seen_last_update = true;
 246         read = 0;
 247         ret = 0;
 248         while (count) {
 249                 char *con_buf0, *con_buf_start;
 250                 long this_round, size;
 251                 ssize_t orig_count;
 252                 long p = pos;
 253
 254                 /* Check whether we are above size each round,
 255                  * as copy_to_user at the end of this loop
 256                  * could sleep.
 257                  */
 258                 size = vcs_size(inode);
 259                 if (size < 0) {
 260                         if (read)
 261                                 break;
 262                         ret = size;
 263                         goto unlock_out;
 264                 }
 265                 if (pos >= size)
 266                         break;
 267                 if (count > size - pos)
 268                         count = size - pos;
 269
 270                 this_round = count;
 271                 if (this_round > CON_BUF_SIZE)
 272                         this_round = CON_BUF_SIZE;
 273
 274                 /* Perform the whole read into the local con_buf.
 275                  * Then we can drop the console spinlock and safely
 276                  * attempt to move it to userspace.
 277                  */
 278
 279                 con_buf_start = con_buf0 = con_buf;
 280                 orig_count = this_round;
 281                 maxcol = vc->vc_cols;
 282                 if (!attr) {
 283                         org = screen_pos(vc, p, viewed);
 284                         col = p % maxcol;
 285                         p += maxcol - col;
 286                         while (this_round-- > 0) {
 287                                 *con_buf0++ = (vcs_scr_readw(vc, org++) & 0xff);
 288                                 if (++col == maxcol) {
 289                                         org = screen_pos(vc, p, viewed);
 290                                         col = 0;
 291                                         p += maxcol;
 292                                 }
 293                         }
 294                 } else {
 295                         if (p < HEADER_SIZE) {
 296                                 size_t tmp_count;
 297
 298                                 con_buf0[0] = (char)vc->vc_rows;
 299                                 con_buf0[1] = (char)vc->vc_cols;
 300                                 getconsxy(vc, con_buf0 + 2);
 301
 302                                 con_buf_start += p;
 303                                 this_round += p;
 304                                 if (this_round > CON_BUF_SIZE) {
 305                                         this_round = CON_BUF_SIZE;
 306                                         orig_count = this_round - p;
 307                                 }
 308
 309                                 tmp_count = HEADER_SIZE;
 310                                 if (tmp_count > this_round)
 311                                         tmp_count = this_round;
 312
 313                                 /* Advance state pointers and move on. */
 314                                 this_round -= tmp_count;
 315                                 p = HEADER_SIZE;
 316                                 con_buf0 = con_buf + HEADER_SIZE;
 317                                 /* If this_round >= 0, then p is even... */
 318                         } else if (p & 1) {
 319                                 /* Skip first byte for output if start address is odd
 320                                  * Update region sizes up/down depending on free
 321                                  * space in buffer.
 322                                  */
 323                                 con_buf_start++;
 324                                 if (this_round < CON_BUF_SIZE)
 325                                         this_round++;
 326                                 else
 327                                         orig_count--;
 328                         }
 329                         if (this_round > 0) {
 330                                 unsigned short *tmp_buf = (unsigned short *)con_buf0;
 331
 332                                 p -= HEADER_SIZE;
 333                                 p /= 2;
 334                                 col = p % maxcol;
 335
 336                                 org = screen_pos(vc, p, viewed);
 337                                 p += maxcol - col;
 338
 339                                 /* Buffer has even length, so we can always copy
 340                                  * character + attribute. We do not copy last byte
 341                                  * to userspace if this_round is odd.
 342                                  */
 343                                 this_round = (this_round + 1) >> 1;
 344
 345                                 while (this_round) {
 346                                         *tmp_buf++ = vcs_scr_readw(vc, org++);
 347                                         this_round --;
 348                                         if (++col == maxcol) {
 349                                                 org = screen_pos(vc, p, viewed);
 350                                                 col = 0;
 351                                                 p += maxcol;
 352                                         }
 353                                 }
 354                         }
 355                 }
 356
 357                 /* Finally, release the console semaphore while we push
 358                  * all the data to userspace from our temporary buffer.
 359                  *
 360                  * AKPM: Even though it's a semaphore, we should drop it because
 361                  * the pagefault handling code may want to call printk().
 362                  */
 363
 364                 console_unlock();
 365                 ret = copy_to_user(buf, con_buf_start, orig_count);
 366                 console_lock();
 367
 368                 if (ret) {
 369                         read += (orig_count - ret);
 370                         ret = -EFAULT;
 371                         break;
 372                 }
 373                 buf += orig_count;
 374                 pos += orig_count;
 375                 read += orig_count;
 376                 count -= orig_count;
 377         }
 378         *ppos += read;
 379         if (read)
 380                 ret = read;
 381 unlock_out:
 382         console_unlock();
 383         free_page((unsigned long) con_buf);
 384         return ret;
 385 }
 386
 387 static ssize_t
 388 vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 389 {
 390         struct inode *inode = file->f_path.dentry->d_inode;
 391         unsigned int currcons = iminor(inode);
 392         struct vc_data *vc;
 393         long pos;
 394         long attr, size, written;
 395         char *con_buf0;
 396         int col, maxcol, viewed;
 397         u16 *org0 = NULL, *org = NULL;
 398         size_t ret;
 399         char *con_buf;
 400
 401         con_buf = (char *) __get_free_page(GFP_KERNEL);
 402         if (!con_buf)
 403                 return -ENOMEM;
 404
 405         pos = *ppos;
 406
 407         /* Select the proper current console and verify
 408          * sanity of the situation under the console lock.
 409          */
 410         console_lock();
 411
 412         attr = (currcons & 128);
 413         ret = -ENXIO;
 414         vc = vcs_vc(inode, &viewed);
 415         if (!vc)
 416                 goto unlock_out;
 417
 418         size = vcs_size(inode);
 419         ret = -EINVAL;
 420         if (pos < 0 || pos > size)
 421                 goto unlock_out;
 422         if (count > size - pos)
 423                 count = size - pos;
 424         written = 0;
 425         while (count) {
 426                 long this_round = count;
 427                 size_t orig_count;
 428                 long p;
 429
 430                 if (this_round > CON_BUF_SIZE)
 431                         this_round = CON_BUF_SIZE;
 432
 433                 /* Temporarily drop the console lock so that we can read
 434                  * in the write data from userspace safely.
 435                  */
 436                 console_unlock();
 437                 ret = copy_from_user(con_buf, buf, this_round);
 438                 console_lock();
 439
 440                 if (ret) {
 441                         this_round -= ret;
 442                         if (!this_round) {
 443                                 /* Abort loop if no data were copied. Otherwise
 444                                  * fail with -EFAULT.
 445                                  */
 446                                 if (written)
 447                                         break;
 448                                 ret = -EFAULT;
 449                                 goto unlock_out;
 450                         }
 451                 }
 452
 453                 /* The vcs_size might have changed while we slept to grab
 454                  * the user buffer, so recheck.
 455                  * Return data written up to now on failure.
 456                  */
 457                 size = vcs_size(inode);
 458                 if (size < 0) {
 459                         if (written)
 460                                 break;
 461                         ret = size;
 462                         goto unlock_out;
 463                 }
 464                 if (pos >= size)
 465                         break;
 466                 if (this_round > size - pos)
 467                         this_round = size - pos;
 468
 469                 /* OK, now actually push the write to the console
 470                  * under the lock using the local kernel buffer.
 471                  */
 472
 473                 con_buf0 = con_buf;
 474                 orig_count = this_round;
 475                 maxcol = vc->vc_cols;
 476                 p = pos;
 477                 if (!attr) {
 478                         org0 = org = screen_pos(vc, p, viewed);
 479                         col = p % maxcol;
 480                         p += maxcol - col;
 481
 482                         while (this_round > 0) {
 483                                 unsigned char c = *con_buf0++;
 484
 485                                 this_round--;
 486                                 vcs_scr_writew(vc,
 487                                                (vcs_scr_readw(vc, org) & 0xff00) | c, org);
 488                                 org++;
 489                                 if (++col == maxcol) {
 490                                         org = screen_pos(vc, p, viewed);
 491                                         col = 0;
 492                                         p += maxcol;
 493                                 }
 494                         }
 495                 } else {
 496                         if (p < HEADER_SIZE) {
 497                                 char header[HEADER_SIZE];
 498
 499                                 getconsxy(vc, header + 2);
 500                                 while (p < HEADER_SIZE && this_round > 0) {
 501                                         this_round--;
 502                                         header[p++] = *con_buf0++;
 503                                 }
 504                                 if (!viewed)
 505                                         putconsxy(vc, header + 2);
 506                         }
 507                         p -= HEADER_SIZE;
 508                         col = (p/2) % maxcol;
 509                         if (this_round > 0) {
 510                                 org0 = org = screen_pos(vc, p/2, viewed);
 511                                 if ((p & 1) && this_round > 0) {
 512                                         char c;
 513
 514                                         this_round--;
 515                                         c = *con_buf0++;
 516 #ifdef __BIG_ENDIAN
 517                                         vcs_scr_writew(vc, c |
 518                                              (vcs_scr_readw(vc, org) & 0xff00), org);
 519 #else
 520                                         vcs_scr_writew(vc, (c << 8) |
 521                                              (vcs_scr_readw(vc, org) & 0xff), org);
 522 #endif
 523                                         org++;
 524                                         p++;
 525                                         if (++col == maxcol) {
 526                                                 org = screen_pos(vc, p/2, viewed);
 527                                                 col = 0;
 528                                         }
 529                                 }
 530                                 p /= 2;
 531                                 p += maxcol - col;
 532                         }
 533                         while (this_round > 1) {
 534                                 unsigned short w;
 535
 536                                 w = get_unaligned(((unsigned short *)con_buf0));
 537                                 vcs_scr_writew(vc, w, org++);
 538                                 con_buf0 += 2;
 539                                 this_round -= 2;
 540                                 if (++col == maxcol) {
 541                                         org = screen_pos(vc, p, viewed);
 542                                         col = 0;
 543                                         p += maxcol;
 544                                 }
 545                         }
 546                         if (this_round > 0) {
 547                                 unsigned char c;
 548
 549                                 c = *con_buf0++;
 550 #ifdef __BIG_ENDIAN
 551                                 vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff) | (c << 8), org);
 552 #else
 553                                 vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff00) | c, org);
 554 #endif
 555                         }
 556                 }
 557                 count -= orig_count;
 558                 written += orig_count;
 559                 buf += orig_count;
 560                 pos += orig_count;
 561                 if (org0)
 562                         update_region(vc, (unsigned long)(org0), org - org0);
 563         }
 564         *ppos += written;
 565         ret = written;
 566         if (written)
 567                 vcs_scr_updated(vc);
 568
 569 unlock_out:
 570         console_unlock();
 571         free_page((unsigned long) con_buf);
 572         return ret;
 573 }
 574
 575 static unsigned int
 576 vcs_poll(struct file *file, poll_table *wait)
 577 {
 578         struct vcs_poll_data *poll = vcs_poll_data_get(file);
 579         int ret = DEFAULT_POLLMASK|POLLERR|POLLPRI;
 580
 581         if (poll) {
 582                 poll_wait(file, &poll->waitq, wait);
 583                 if (poll->seen_last_update)
 584                         ret = DEFAULT_POLLMASK;
 585         }
 586         return ret;
 587 }
 588
 589 static int
 590 vcs_fasync(int fd, struct file *file, int on)
 591 {
 592         struct vcs_poll_data *poll = file->private_data;
 593
 594         if (!poll) {
 595                 /* don't allocate anything if all we want is disable fasync */
 596                 if (!on)
 597                         return 0;
 598                 poll = vcs_poll_data_get(file);
 599                 if (!poll)
 600                         return -ENOMEM;
 601         }
 602
 603         return fasync_helper(fd, file, on, &poll->fasync);
 604 }
 605
 606 static int
 607 vcs_open(struct inode *inode, struct file *filp)
 608 {
 609         unsigned int currcons = iminor(inode) & 127;
 610         int ret = 0;
 611
 612         tty_lock();
 613         if(currcons && !vc_cons_allocated(currcons-1))
 614                 ret = -ENXIO;
 615         tty_unlock();
 616         return ret;
 617 }
 618
 619 static int vcs_release(struct inode *inode, struct file *file)
 620 {
 621         struct vcs_poll_data *poll = file->private_data;
 622
 623         if (poll)
 624                 vcs_poll_data_free(poll);
 625         return 0;
 626 }
 627
 628 static const struct file_operations vcs_fops = {
 629         .llseek         = vcs_lseek,
 630         .read           = vcs_read,
 631         .write          = vcs_write,
 632         .poll           = vcs_poll,
 633         .fasync         = vcs_fasync,
 634         .open           = vcs_open,
 635         .release        = vcs_release,
 636 };
 637
 638 static struct class *vc_class;
 639
 640 void vcs_make_sysfs(int index)
 641 {
 642         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, index + 1), NULL,
 643                       "vcs%u", index + 1);
 644         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, index + 129), NULL,
 645                       "vcsa%u", index + 1);
 646 }
 647
 648 void vcs_remove_sysfs(int index)
 649 {
 650         device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 1));
 651         device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 129));
 652 }
 653
 654 int __init vcs_init(void)
 655 {
 656         unsigned int i;
 657
 658         if (register_chrdev(VCS_MAJOR, "vcs", &vcs_fops))
 659                 panic("unable to get major %d for vcs device", VCS_MAJOR);
 660         vc_class = class_create(THIS_MODULE, "vc");
 661
 662         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 0), NULL, "vcs");
 663         device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 128), NULL, "vcsa");
 664         for (i = 0; i < MIN_NR_CONSOLES; i++)
 665                 vcs_make_sysfs(i);
 666         return 0;
 667 }